1. Field of the Invention
The invention relates to a polyimide polymer, a polyimide film, and a flexible copper-coated laminate. More particularly, the invention relates to a polyimide polymer having a low dielectric constant, a polyimide film including the polyimide polymer, and a flexible copper-coated laminate including the polyimide film.
2. Description of Related Art
As electronic devices gradually become thinner and lighter, the demand for use of a flexible printed circuit board greatly increases. The mainly upstream material of the flexible printed circuit board is a flexible copper-coated laminate which is produced by coating or attaching a polyimide polymer onto a copper foil. In the current industry environment, the polyimide polymer is required to have a low dielectric constant, high thermal stability, and a coefficient of thermal expansion close to that of the copper foil. However, in the related art, through introducing fluorine-contained functional group into the polyimide polymer or introducing adamantane into the aliphatic polyimide polymer, the polyimide polymer can have a reduced dielectric constant but cannot have improved thermal stability and a proper coefficient of thermal expansion. Therefore, developing a polyimide polymer having a low dielectric constant, high thermal stability, and a coefficient of thermal expansion close to that of the copper foil is one of the desired goals to those skilled in the art.